In the field of metallurgy, it is advantageous to provide high strength, high conductivity, copper-base alloys. It is also advantageous to provide a method for producing high tensile strength, high electrical conductivity, copper-base alloys, and copper alloy plate, in an economical manner with desirable fabrication characteristics for making electrical or electronic parts.
To this end, copper by itself has excellent electrical conductivity and other characteristics. However, copper by itself is deficient in tensile strength for many applications. Thus, extensive research has long been undertaken to increase the tensile strength of the copper by adding alloying elements thereto, such as tin, manganese, silver, zinc, cobalt, titanium, chrominum and zirconium. In particular, the tensile strength of the copper has been increased by adding tin as an alloy element, as described in Japanese Patent Applications Nos. 52-78621 and 53-89662, as well as U.S. Pat. No. 4,337,089. However, the electrical conductivity of the resulting alloys has been so reduced that these alloys have not been suitable for the lead frames of transistors or integrated circuit, which require a high tensile strength and a high electrical conductivity respectively. These tensile strengths are in the range of greater than at least about 40 kg/mm.sup.2. These electrical conductivities have been in the range of at least about 60% or more of the conductivity of pure copper, which is referred to as a conductivity percent IACS, as referred to in the above mentioned U.S. Pat. No. 4,337,089.
It has also been advantageous to improve the fabrication characteristics and the method for making copper-nickel alloys by reducing the brittleness and the hot working steps known heretofore, and/or by reducing the poor workability in the heretofore known reduction ratios of the cold working, which resulted from adding such alloying elements as tin, or too much of some other elements, such as the above mentioned elements.
It has still further been advantageous to reduce the cost of the cooper-nickel alloys heretofore by eliminating expensive alloying elements, such as tin and/or manganese, by reducing the amounts of the additives, and/or by finding cheaper additives.
Still further, it has been advantageous to improve the elongation characteristics of the copper-nickel alloys known heretofore for the above mentioned applications, including the mentioned lead frames for transistors and/or integrated circuits.